1. Field of the Invention
The present invention relates generally to a method of erasing data from an optical disc, and, more particularly, to a method and device for efficiently erasing data that is recorded on an optical disc that can be written once such as a Write Once Read Many (WORM) disc.
2. Description of the Related Art
After Compact Discs (CDs), that is, optical recording media capable of recording 74 minutes of music or about 650 Mbytes of data, were commercialized, Digital Versatile Discs (DVDs) capable of recording a 2-hour Standard Definition (SD)-class movie were widely commercialized, and Blu-ray Discs (BDs) and High-Density Digital Versatile Discs (HD-DVDs) capable of recording a High Definition (HD)-class movie will appear on the market in the near future.
Optical recording media, such as CDs, DVDs and BDs, are disc-shaped media for recording data using optical characteristics, and data can be written on the discs and read from the discs using optical pickups. Optical recording media include recorded discs for reproduction on which data is recorded already, and discs for recording, such as CD-R/RW, DVD-R/+R/-RW/+RW/RAM and BD-R/-RE media, that can be written or rewritten.
Among the discs for recording, discs such as CD-R and DVD-R/+R media are WORM discs, meaning that they can be written once and do not support the modification or deletion of previously stored data, from the aspect of disc specifications.
Accordingly, methods of preventing WORM discs, which store sensitive data not to be exposed to the outside, from being read or methods of deleting such data from the WORM discs have been proposed.
As an example, as shown in FIG. 1, there is a method of overwriting only navigation information stored in the Lead In Area (LIA) of an optical WORM disc and only file system information stored in the File System Information Area (FMIA) of the optical WORM disc with arbitrary null data.
As a result, the navigation information and file system information, necessary to control the reading of the data stream stored in the data area of the optical WORM disc, cannot be used further, which has the effect of the data stream recorded in the data area of the optical disc being indirectly erased or not accessible.
There is another method of achieving the effect of deleting a data stream stored in the data area of an optical disc by deleting only an encryption key necessary for decryption of the encrypted data stream into the original data stream by overwriting the encryption key with arbitrary null data, in the case where the data stream is recorded in the data area of an optical WORM disc in an encrypted state, as shown in FIG. 2.
Still in another method, a user forms scratches on an optical disc, particularly in the LIA thereof, using a mechanical tool, or an optical disc is physically damaged using a heater or a compressor, as shown in FIG. 3, has been proposed.
However, in the above case where only the navigation information and file system information, or only the encryption key is erased, a problem arises in that a data stream recorded in the data area of the disc still exists without change, so that the data stream may be leaked through hacking or the like. In the other case where the optical disc is damaged using a mechanical tool, a heater, or a compressor, problems arise in that inconvenience in use is caused and additional high-cost equipment may be required.